Inventories and fluxes of 210Pb, 137Cs and 241Am determined from the soils of three small catchments in Cumbria, UK

J. T. Smith*, P. G. Appleby, J. Hilton, N. Richardson

*Corresponding author for this work

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Inventories and vertical profiles of fall-out 210Pb, 137Cs (both weapons test and Chernobyl) and 241Am (a decay product of 241Pu) have been measured in the soils of three catchments in Cumbria, UK. Soil types varied from mineral soils to highly organic peat bog. The 210Pb inventories in different cores from the same catchment were relatively uniform, the standard deviation of measurements being around 30%. Mean annual fluxes of 210Pb were calculated from the soil inventories were 63 Bq m-2 year-1 (Brotherswater catchment), 63 Bq m-2 year-1 (Blelham Tarn catchment), and 97 Bq m-2 year-1 (Devoke Water catchment) per metre of rainfall. From these and earlier data published in the literature, the mean UK 210Pb flux is estimated to be 77 ± 14 Bq m-2 year-1 per metre of rainfall. Inventories of 137Cs (weapons test and Chernobyl) were more variable, but mean values for each of the catchments were in agreement with independent studies. The mean weapons test deposition (decay corrected to 1986) was 2790 Bq m-2 per metre of rainfall, compared to UK average of 3160 Bq m-2 derived from extensive national surveys. Although 241Am levels in Brotherswater soils were comparable with those expected from weapons test fall-out, significantly higher values were recorded at Blelham Tarn and Devoke Water. Well-resolved peaks in 241Am activity some distance below the present surface suggest that this radionuclide is relatively immobile within the soil column. The depth of penetration of 75% of the inventory into the soil column was similar for 210Pb, 137Cs (weapons) and 241Am, all being significantly greater than Chernobyl 137Cs. The vertical profiles of 137Cs (weapons) suggest that there has been little mobility during the 15 years since a previous study (Cawse 1983).

Original languageEnglish
Pages (from-to)127-142
Number of pages16
JournalJournal of Environmental Radioactivity
Issue number2
Publication statusPublished - 1 Nov 1997


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